[Stoves] Request to get partners in a possible TLUD stove improvement project
kgharris
kgharris at sonic.net
Wed Aug 5 01:59:02 CDT 2015
All,
These are good discussions on burning CO and swirl. I know that Aprovecho has developed a good charcoal stove based on experimentation by labratory manager Sam Bentson. My own experience is much less but I do see in my TLUD combustor blue CO flames in the Venturi gas mixer after the hydrocarbon flames have gone out. I do not know how thurough this burning of CO is. My speculation is that thoroughly mixing adiquate air with the CO, and keeping a flame going above the coals, as per Sam's findings, does a good job of burning CO for those who want to burn the char.
Swirl is a method I use for getting more dwell time for the flame in the combustor section of the stove. Swirl is not used for mixing because the gasses are thuroughly mixed by the Venturi gas mixer before they pass through the stationary fan. Also swirl is not a good mixing method because it will seperate cooler denser gasses from hotter less dense gasses like a centrifuge. I do not use turbulance for mixing because I believe the Venturi method is more thorough, though I agree with Dr. Larson that adding turbulance will improve combustion in a non-Venturi burner. As with any mixing method, the Venturi method can be overwhelmed if to much wood gas is run through it, in agreement with Dean Still's statements. So far my 6' diameter combustor can operate efficiently up to about 3 kw. Above this both the mixer and stationary fan are not adiquate. Adding more mixing capacity by adding more Venturi mixers helps with mixing, as three stove camp participants who helped me, Roberto, Steve and Cody showed me last week at Aprovecho's stove camp.
The stationary fan has 6 blades and the shape of each blade is a smooth curve. By the Coanda effect a flame up to 3kw can cling to the back side of the blade and leave the blade's trailing edge at a good flat angle. A higher power flame produces so much buoyancy that the flame is seperated from the blade early and goes off at a fairly steep, not so good angle. A new stationary fan design suggested by Dr. Larson may solve this problem and with additional Venturi mixers give the combustor the capability to handle higher power levels. We shall see.
Best to all,
Kirk
----- Original Message -----
From: Dean Still
To: Discussion of biomass cooking stoves
Sent: Tuesday, August 04, 2015 9:58 PM
Subject: Re: [Stoves] Request to get partners in a possible TLUD stove improvement project
Ron,
IMO, swirl is not as powerful a cleaner stove technique compared to 1,) limiting the rate of woodgas being made or 2.) the generated mixing ability. We start by limiting the rate of reactions by decreasing primary air. Then add higher velocity jets of secondary air.
Swirl is great but I think that it is gravy. May be wrong!
Best,
Dean
On Tue, Aug 4, 2015 at 6:13 PM, Ronal W. Larson <rongretlarson at comcast.net> wrote:
Dean:
I want to emphasize - no making of a new stove intended. This is to be only an addition to stoves that (hopefully, but not necessarily) have already been tested. Looking for a breadth of existing designs. Hopefully these are already in the best “balance” they could achieve. This is to see whether that can be improved.
What have you seen in swirl approaches?
What have you seen in turbulence enhancers?
Thanks for the quick feedback.
Ron
On Aug 4, 2015, at 6:52 PM, Dean Still <deankstill at gmail.com> wrote:
Hi Ron,
In my opinion, reducing emissions in a TLUD or any stove requires testing with emissions equipment. The great stove combines many factors working together. "Swirl" is only one part. Kirk gets good results when everything is in balance. "Swirl" is not powerful enough to overcome problems in the balance.
I completely agree that anyone with tin snips and emission equipment and perseverance can make low emission stoves. If you are lucky it takes a shorter time. So what? Even if you are unlucky it happens eventually. Drink more coffee.
Best,
Dean
On Tue, Aug 4, 2015 at 5:40 PM, Ronal W. Larson <rongretlarson at comcast.net> wrote:
Stove list cc Kirk
From what I can understand, the lowest emission (particulates, CO is easy) values from TLUDs have been from stoves designed and tested (last week) by Kirk Harris. One reason seems to be that he has achieved a swirl, using (as described on this list often) a fan blade shape.
I recall a few other uses of the term “swirl”, but know of no significant tests like those by Kirk.
In recent conversations, Kirk has agreed to be part of an off-list TLUD stove group to investigate a different means of achieving swirl. It seems to be cheap and applicable to most TLUD stoves.
The main advantage of a swirl is more flame time spent in the stove; to get low emissions, hot gases, not flames, need to be hitting the cook pot.
The proposed approach also should increase turbulence. I do not recall any TLUD that tried to achieve turbulence (to get the mixing needed for shorter path lengths and more complete combustion). Anybody know of designs to achieve turbulence other than added disk or washer shapes?
The reason for not saying much now is to save list members’ time and energy. This is not a guaranteed approach.
Anyone joining should want to see this open-source (no patents).
Anticipated time commitment for a first design - a few hours with tin snips. Metal cost a buck or two. Probably can work with clay as well.
If anyone knows of past swirl or turbulence experiments (or modeling) in TLUDs, your input now could save Kirk and I (and anyone else wanting to join) a lot of time - especially if those results were negative.
Ron
feel free to call 303-526-9629, if that would help.
_______________________________________________
Stoves mailing list
to Send a Message to the list, use the email address
stoves at lists.bioenergylists.org
to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
for more Biomass Cooking Stoves, News and Information see our web site:
http://stoves.bioenergylists.org/
--
Dean Still
Executive Director
Aprovecho Research Center
PO Box 1175
76132 Blue Mountain School Road
Cottage Grove, OR 97424
(541) 767-0287
_______________________________________________
Stoves mailing list
to Send a Message to the list, use the email address
stoves at lists.bioenergylists.org
to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
for more Biomass Cooking Stoves, News and Information see our web site:
http://stoves.bioenergylists.org/
_______________________________________________
Stoves mailing list
to Send a Message to the list, use the email address
stoves at lists.bioenergylists.org
to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
for more Biomass Cooking Stoves, News and Information see our web site:
http://stoves.bioenergylists.org/
--
Dean Still
Executive Director
Aprovecho Research Center
PO Box 1175
76132 Blue Mountain School Road
Cottage Grove, OR 97424
(541) 767-0287
------------------------------------------------------------------------------
_______________________________________________
Stoves mailing list
to Send a Message to the list, use the email address
stoves at lists.bioenergylists.org
to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
for more Biomass Cooking Stoves, News and Information see our web site:
http://stoves.bioenergylists.org/
------------------------------------------------------------------------------
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2015.0.6086 / Virus Database: 4392/10374 - Release Date: 08/05/15
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20150804/c3d5441e/attachment.html>
More information about the Stoves
mailing list